Metal-oxide-semiconductor field-effect transistors (FETs or MOSFETs) are widely used in integrated circuits (ICs). To increase the density of MOSFETs in ICs, physical dimensions such as gate length LG of MOSFETs are aggressively reduced. MOSFETs with short LG may suffer from undesirable short-channel effects (SCEs), such as high off-state leakage current and high drain-induced barrier lowering.
To suppress SCEs in transistors having short gate lengths LG, the multiple-gate field-effect transistor (MuGFET) architecture may be employed. A MuGFET has better electrostatic control of the channel potential by the gate electrode, as compared to a planar device structure. MuGFETs include examples such as the double-gate transistor and tri-gate or triple-gate transistor. A double-gate transistor is also known as a double-gate FinFET. A tri-gate transistor may be referred to as tri-gate FinFET, or simply FinFET. Double-gate or tri-gate devices employ a channel that resembles a fin. The on-state or saturation drive current IDsat flows in a fin to achieve high current density per footprint or layout area.
Other MuGFETs include pi-gate, omega-gate, surround-gate (SG) or gate-all-around (GAA) structure, where the electrostatic gate control is further improved. The SG transistor has a channel that is similar to a nanowire, where the nanowire may be oriented horizontally or vertically. For a horizontal nanowire transistor, several horizontally-oriented nanowire channels may be vertically stacked.